The proposed research is a continuation of studies completed and in progress which are designed to evaluate insulin action in the liver in normal and altered metabolic states. The specific aims are to further characterize insulin action in the liver with regard to the acute and chronic effects of insulin on lipoprotein synthesis and secretion and the role of insulin resistance in altering insulin action on these parameters. We will further explore the role of glucocorticoids in modulating insulin action in regard to glycogen synthesis and lipid and apo B synthesis and secretion. Additional studies will include and evaluation of phosphorylation events in insulin action with regard to the phosphorylation of apo B by acute and chronic changes in insulin levels in vitro and in vivo. The role of the insulin receptor in phosphorylation of apo B will also be evaluated. Finally, we will pursue ongoing studies to evaluate the mechanisms of insulin resistance in nonketotic streptozotocin-induced diabetes mellitus by testing the hypothesis that the insulin receptor kinase is under intracellular regulation and is not identical in all subcellular fractions. Methodologies to be employed included primary cultures of rat hepatocytes, subcellular fractionation of rat liver, affinity chromatography of the insulin receptor, insulin receptor autophosphorylation and tyrosine kinase activity, synthesis of lipid using 3H20 and 14C- acetate, net glycogen production, 35S-methionine incorporation into apo B, apo B mass measurements by radioimmunoassay, SDS PAGE, 32P incorporation into apo B using immunoprecipitation and SDS PAGE, phosphoamino acid analysis, HPLC, and lipid mass measurements by TLC. The proposed studies will improve our understanding of insulin mediated hepatic metabolism and the interrelationships between insulin and glucocorticoids with regard to lipid, glycogen, and apo B metabolism. In addition, the proposed studies of insulin action in normal and altered metabolic states will allow us to better define mechanisms of insulin action and the pathophysiology of a group of disorders characterized by insulin "resistance". Because of the central role of the liver in lipoprotein production and metabolism and the importance of lipoproteins in the development of atherosclerosis in Type II diabetes, an improved understanding of insulin effects on lipoprotein synthesis and secretion will enable us to mechanistically approach the relationships between diabetes and atherosclerosis.